Determine If Last Character is Number or Not A Number

Hey folks,

I'm trying to determine if the last character of a cell is a number or not a number. So in a cell I may have a string like:

ZXC123

or

ZXC123A

If the last character is not a number I want the letter returned. So I thought I could use a formula like:

=IF(NOT(ISNUMBER(RIGHT(D88,1))), RIGHT(D88,1),"")

However for the string ZXC123 it still returns '3' so anyone have any ideas how I can do this?